TLC, yes, ruminating is no fun is it. I think with dysfunctional relationships in particular this is the brain's way of saying - what the hell? Our brains like for things to make sense.
I read back on your other threads to refresh my memory and you had this long term relationship with someone who said - hang in there with me! Don't give up! Telling you he loves you etc.
On the flip side he keeps drinking and immediately moves on to a new relationship (with someone he drinks with).
In the normal world this doesn't make sense. When someone sincerely says, hang in there with me, that means you are in it together and going to make it work no matter what and that effort will show.
Now, I'm sure he must have had some good qualities or you wouldn't have gotten involved with him, however that then devolved in to drunken name calling (abuse).
Hard to rationalize love and abuse. It does not make sense.
I am guessing you have read all the stickies about alcoholism, abuse etc? If not, please do. Knowledge is power and reading those may give you the framework for the answers you are looking for and help with some of that rumination.
The second thing and I've done this and seen others here mention it is to stop yourself with a set plan of something to do. This takes repetition (so don't give up on it!). Once you have sought the knowledge - that won't stop the rumination completely, it just quietens it a bit. Then it's time to take action (well actually now is the time to start) when you start to ruminate stop yourself. If that means saying "stop" out-loud to yourself, so be it, if it means snapping a rubber-band you have on your wrist - then that's what you need to do, If it means watching a movie, watch action films (even if you don't like them much) whatever you think will work for you. It can be hard to focus on something as long as a movie, just keep pulling your mind back to the movie.